3/3 I realized this after spending some time improving my layout for the medium layout and checking it on a single device. We should design layouts based on screen sizes, not device types.

Does your application support foldable devices?

2/3 Here's the problem:
Google's window size classes aren't device categories—they're viewport measurements. The Pixel 9 Pro Fold jumps straight from compact to expanded, never using medium.

On the other side, Samsung's Z Fold 5 uses medium.

Same device category, but different screen sizes.

Your preview functions can be used not only for development but also as a tool to releasing apps without pixel imperfections.

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You now need only to make minor adjustments to implement visual tests.

Start strategically:
• Convert your design system and/or common components first
• Add preview functions for the most critical screens
• Gradually expand coverage to less critical screens

But if you are already using Jetpack Compose, you can use ComposablePreviewScanner or the Compose Preview Screenshot Testing framework to transform your preview functions into visual tests.

You likely already created a preview function, which was the hard part.

3. Number formatting varies between countries.

Let's compare:

• US: 12,345,678.9
• FR: 12 345 678,9

Use "NumberFormat.getNumberInstance(locale)." for number formatting.

Which of these has caused issues in your apps?

2. Date formats are often a reason for user confusion.

Is "01/02/2025" January 2nd or February 1st? Actually, it depends on the locale.

• US: MM/DD/YYYY
• UK: DD/MM/YYYY

Use "DateTimeFormatter" to format dates based on locale.

Apply a similar approach to time formatting.

1. Currency formatting differs by country:

• US: $1,234.56
• DE: 1.234,56 €

Use "NumberFormat.getCurrencyInstance(locale)" for proper currency symbol positioning.

Documentation: developer.android.com/reference/k...

Add this dependency to use the component:
implementation("androidx.compose.material3:material3-android:1.4.0-alpha15")